This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and thus not compensated for and can thin the engine out and can plus permit the engine to rev taking place once not desired causing prickly running. As its a mechanical defect it tends not to outlook upon the deformity fresh and you can sometimes hear a hissing noise later the engine running.
Its as well as worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a sick pump will every outcome in insufficient fuel brute delivered to the engine. Might moreover be worth cleaning out the idle zeal direct motor / valve as these get clogged up next carbon and some brake cleaner washed through helps clear things off.
in the same way as I begin the car, the engine surges taking place amid 1200 and 2000 rpm incite and forth. I misrepresented the IAC and the TPS in imitation of no alter in symptoms. I have noticed that several Lexus SC's have this thesame issue. Prior to this I would have to familiarize the idle enthusiasm screw to degrade the rpm and it would maintain for a while. Now, the engine is for ever and a day surging to the lessening where I cannot steer it for dread of broken to the drive train. Any experienced solution?